Method for making electric discharge device

ABSTRACT

A NOVEL METHOD FOR MAKING A DISCHARGE DEVICE, PARTICULARLY A HIGH VOLTAGE RECTIFIER, WHICH COMPRISES AN ANODE AND A CATHODE ENCLOSED IN A GLASS ENVELOPE WITH CONDUCTIVE LEADS SEALED THROUGH THE ENVELOPE FOR MAKING ELECTRICAL CONNECTION TO THE ANODE AND CATHODE. AT LEAST ONE OF THE LEADS COMPRISES A HOLLOW TUBULAR MEMBER HAVING A CLOSED END CONTAINED IN THE ENVELOPE AND AN OPEN END SEALED TO THE ENVELOPE AND FORMING A FEMALE SOCKET FOR ELECTRICAL CONNECTION THERETO.

United States Patent Cletus E. Maier Cannelton, Ind. [211 App]. No. 810,896

122] Filed Jan. 30, 1969 [45] Patented June 28, 1971 [72] Inventor [54] METHOD FORMAKING ELECTRIC DISCHARGE DEVICE 1 Claim, 9 Drawing Figs.

[52] 11.8.0 29/25J5, 29/25.13, 29/4729 [51] lnt.Cl 1101 9/18, H01j 9/36 [50] Field otSearch 29/25.13, 25.15,25.11,472.9,25.16

[56] References Cited UNITED STATES PATENTS 2,473,969 6/1949 Pryslale et a1 29/25.l5X

2,532,846 12/1950 Jonker 29/25.]5 2,647,298 8/1953 Pryslak et al. 29/25.]5 2,699,516 1/1955 Deimer et al. 29/25.16X 3,408,719 11/1968 Van Sickler etal.... 29/25.]5 3,480,823 11/1969 Cheng-lin Chen 29/472.9X

Primary Examiner-John F. Campbell Assistant ExaminerRichard Bernard Lazarus Attorneys-Nathan .l. Cornfeld, Henry T. Olsen, Frank L.

Neuhauser and Oscar B. Waddcll ABSTRACT: A novel method for making a discharge device, particularly a high voltage rectifier, which comprises an anode and a cathode enclosed in a glass envelope with conductive leads sealed through the envelope for making electrical connection to the anode and cathode. At least one of the leads comprises a hollow tubular member having a closed end contained in the envelope and an open end sealed to the envelope and forming a female socket for electrical connection thereto.

PATENIED JUH28 I971 SHEET 1 OF 2 PATENTEU JUN28 I971 SHEET 2 [1F 2 FIG.5.

'IFIG.4.

FIG.9.

FIG.8.

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INVENTORZ CLETUS E. MAIER WM 7 3" BY ms ATTORN METHOD FOR MAKING ELECTRIC DISCHARGE DEVICE This invention relates to electric discharge devices, and more particularly to high voltage discharge devices, such as high voltage rectifiers.

In high voltage devices it is necessary that the external leads which connect to the electrodes within the device be spaced sufficiently far apart so that corona or arcing is prevented. Thus, in the usual high voltage rectifier the cathode is connected to the external circuit through lead pins sealed through the base of the envelope while the anode lead, or top cap, is sealed through the dome of the envelope. The height of the envelope from base to dome was usually great enough to provide sufi'rcient distance between the cathode and anode leads to avoid corona.

With the need to miniaturize such discharge devices, the height of the envelope has been attempted to be reduced by providing more insulation around the external connections. Such attempts have been relatively uneconomic solutions.

With the need for high voltages to be handled by such devices, particularly for color television receivers, an even greater demand on prevention of corona has been made. To

' merely make the height of the devices great obviates against the need for small devices. A high voltage discharge device which satisfied the above need is disclosed and claimed in coperrding application, Ser. No. 613,338 now U.S. Pat. No. 3,456,147 patented July 15, 1969 and filed herewith and assigned to the same assignee as herein.

An object of this invention is to provide an improved means for sealing the envelope of the aforementioned device. Another object .of the invention is to provide an improved method of manufacture of said device.

In accordance with the aforementioned objects there is provided a high voltage discharge device comprising an anode and cathode mounted in spaced relationship with a sealed insulative envelope, a conductive lead for each of said electrodes sealed in said envelope at opposite ends thereof, one of said leads being a hollow tubular member having an open end and a closed end, said closed end being within said envelope and the edge of said open end being secured to the envelope by a multiple surface seal.

Further objects and advantages of the invention will be understood from the following complete description of the preferred embodiment thereof and from the drawing wherein:

FIG. 1 is a perspective view of an electron discharge device constructed in accordance with the preferred embodiment of the invention;

FIG. 2 is an enlarged section view of a portion of said device;

FIG. 3 is an enlarged section view of the seal;

FIGS. 4-9 are illustrations of the steps in the manufacture of the device.

As shown in FIG. I, a high voltage rectifier incorporating the invention includes a sealed glass envelope 3 of lead or borosilicate glass. Said envelope may have on its interior surface a coating of semiconductive material such as lead or chrome oxide to protect the envelope from ion bombardment. The high voltage discharge device further includes a deep drawn inverted cuplike anode 4 mounted within the envelope and a cathode 5 mounted within the confines if the anode 4. The cathode 5 is mechanically supported, and electrical connection may be made thereto, by a pair of conductive leads 6 and 7. The conductive leads 6 and 7 are sealed in the base portion 8 of the envelope 3 with pins 9 and 10 extending outwardly therefrom for external electrical connection of the cathode 5. While, as shown, the leads 6 and 7 are individually integral conductive members, they may be constructed as a plurality of pieces secured together as by welding. The cathode 5 is illustrated as a filamentary directly heated cathode but may be an indirectly heated cathode as well.

The inverted cuplike anode 4 is supported, and electrical connection thereto may be made, by an anode lead 11 sealed in the opposite end, or dome, 12 of the envelope 3 so that a maximum distance is afforded between the anode lead 11 and the cathode pins 9 and 10 to prevent corona therebetween. The anode lead 11 includes a solid rod, or wire, 13 and a thinwalled tubular cuplike lead shell 14 having an end wall 15 and an open end 16. The rod 13 is secured at its ends to the anode 4 and the anode lead shell 14, respectively, by percussion welds l7 and serves as a low thermal conductivity path therebetween while mechanically and electrically connecting them. The open end 16 of the anode lead shell 14 is secured in the dome 12 of the envelope by a seal 18.

The seal 18 (FIG. 3) is formed around the end edge 16a of open end 16 of the anode lead shell so that it is a multiple surface seal. Thus, as illustrated, the glass of the seal 18 coats, and is fixed to, the outer surface 16b, the inner surface 160, and the end edge 16a, of the open end 16 of the anode lead shell 14. The multiple surface seal 18 has, in addition to the greater seal afforded, the distinctive advantage that no conductive material edge or point is exposed from which a corona discharge could initiate.

The anode lead shell 14 is preferably provided intermediate its ends with a circumferential constriction or rib 19 to constrain movement of the external connector 20 of the type to be used in connecting the anode to the external circuit. The connector 20 as illustrated, can with the high voltage discharge device of the present invention be simply a conductor 21 coated with insulation 22 upon which a conductive end piece 23 has been crimped. The external connector 20 may be pushed into the anode lead shell 14 so that the rib 19 exerts a radial force thereon and prevents its inadvertent withdrawal. The cuplike shape of anode lead shell 14, by extending into the interior of the envelope and surrounding the only exposed conductive part of the connector 20 (the end piece 23), obviates the need for any insulative structure on the connector as was heretofore required. Thus, in effect, the envelope 3 of the discharge device acts as the insulative cover for the external connector as well as the electrodes of the device itself.

The anode 4 and the anode lead 11 can be easily manufactured ,and sealed into the dome 12 of an envelope 3 by first percussively welding the rod 13 to the anode l4 and the anode lead shell 14 as previously indicated. The welds 17 may be made separately or simultaneously. A bulb with the domeintact is then placed over the assembly with the open end 16 of the lead shell 14 in contact with the dome 12 of the bulb (FIG. 4). A centered overhead flame 24 is directed at that portion of the dome which is contacted by the lead assembly. The flame depresses the softened bulb into the interior of the anode lead shell 14 and then pierces it; and the open end 16, being in contact with the interior surface of the dome, confines the piercing to that small portion of the dome (FIG. 5). Continued application of the flame heats the anode lead shell to the proper temperature, approximately 850 C. at which bonding of the glass to the metal will occur. At this temperature a small amount of molten glass flows over the inner and outer surface of the anode lead shell forming the multiple surface seal 18. As the parts are slowly cooled and annealed by annealing flame 25, the anode assembly is pulled downwardly so as to depress the seal 18 approximately 0.100 inch below the surface of the dome (FIG. 6). The base 8 with the cathode pins 9 and I0 sealed therein and cathode 5 mounted upon leads 6 and 7 is sealed to the bottom end of the bulb (FIG. 7) by fires 26. The assembly is completed by heating the electrodes with an induction heating coil 27, particularly the anode 4 so as to cause outgassing of the parts (FIG. 8). During this extensive heating of the anode, the rod 13 prevents sufficient heat from being conducted to the area of the seal 18 to cause rupture thereof. The envelope is exhausted through exhaust head 28 and the tip-off 8a formed to complete the device (FIG. 9).

From the above, it will be seen that there is provided a method of manufacturing a high voltage discharge device which has a reduced height with the anode connection securely sealed to the envelope and with no metal piece extending externally therefrom.

What is claimed as new and desired to be secured by Letters Patent of the U5. is:

I claim:

secured to the envelope by a multiple surface seal around the said open end edge, which method comprises securing the anode to said hollow tubular member, placing an insulative bulb in contact with said hollow tubular member, applying heat to the portion of the bulb in contact with said member, and sealing said bulb to the open end of said member. 

